Book review: ‘The Planet Factory: Exoplanets and the Search for a Second Earth’

A great introduction to a relatively new and fast-changing aspect of scientific endeavour: the search for exoplanets similar to Earth.

Twenty-odd years ago, the word planet referred to nine somewhat distant and mysterious objects in the only known ‘solar system’. Since 1995, however, when the first detection of a planet outside our home system was confirmed, the concept of a planet orbiting another star has morphed from science fiction into fact. Today, according to NASA’s exoplanet website, there are more than 3,500 confirmed exoplanets - 366 of which are “terrestrial” - and our solar system is but one of 2,614. Talk about having to rewrite text books!

In ‘The Planet Factory: Exoplanets and the Search for a Second Earth’ (Bloomsbury Sigma, £16.99, ISBN 9781472917720), astrophysicist Elizabeth Tasker - who spends her time “building fake universes inside a computer” - tells the story of exoplanets and that fabled SF-concept of a “second Earth”. To her, however, these new-found worlds are “more alien than anything in fiction”. She describes exoplanets “larger than Jupiter with years lasting a week; others with two suns lighting their skies [and]… planets with diamond mantles supporting oceans of tar”.

The book is presented in three main sections. The first - ‘The Factory Floor’ - is about the formation of the solar system, which the author compares to a “factory assembly mechanism”. The second describes the discovery process, orbits and composition of some of the more unusual worlds, while the third concludes with the “Goldilocks Worlds”. The latter refers to the so-called “habitable zone” around a star, in which an Earth-like planet may exist. Tasker calls this “possibly one of the most regrettable naming choices in planetary science [because] the name implies planets with crystal-clear lakes, lush greenery and a perfectly-heated, oat-based breakfast”. In fact, she says, it just means that “if the surface were exactly like that of the Earth, your cup of water would stay liquid”.

The book is written in an engaging and informative style and provides a great introduction to a relatively new and fast-changing aspect of scientific endeavour. Importantly, it includes an introductory chapter on detection techniques, such as transit and radial velocity methods, which are described in everyday language. It has a short glossary, an index and a further reading section. And there are the inevitable references to Star Wars when it comes to the ‘Goldilocks’ and ‘Alien Vistas’ sections.

Perhaps the most surprising omission, in such a work of popular science, is the lack of photos or artist’s concepts, illustrative material being restricted to a couple of dozen simple line-diagrams. Significantly, even the cover rejects science-based concepts for a childlike cartoon. While it’s good to find an author who can conjure up an image with her words, the old adage about a picture being worth a thousand of them still applies.

That criticism apart, the study of exoplanets is still in its infancy and this may be the book that gets the next generation of exoplanet researchers fired up about the subject. As the author concludes, confirming life on a planet around another star is a generational task with the complexity of a jigsaw puzzle. The identification of a “second Earth” could, moreover, be crucially important for the future of the human race.

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